In the last week, two companies have broadcast codes that have zapped the hacked smartcards some US and European viewers have been using to get access to TV channels without paying for them.

Outraged pirates and hackers have been flooding discussion groups on the net looking for ways to fix their broken cards.

But the satellite TV companies have pledged to take further action if the hackers find a way to reactivate their cards.

Hacking access

For many years, satellite TV companies and card crackers have been engaged in a battle over the technology, set-top boxes and smartcards, that controls the channels subscribers can view.

The smartcards have a computer processor and small amount of memory on board that lets them be updated remotely and helps them decode the TV signals coming down from a satellite.

Roger Stanyard, managing director of satellite experts DTT consulting, said card crackers had gradually gained the upper hand since 1996 when the first digital satellite TV companies started offering services.

"As things started to go digital, they appeared to be more secure as regards encryption and conditional access," he said. But the crackers have found and exploited loopholes in the cards to get free access to any and every channel broadcast by a satellite TV company.

Airwave action

The cracked cards are widely available via internet websites, auction sites and the classified pages of satellite magazines. Many are sold with guarantees that they will work for at least 12 months.

But now two satellite TV companies are fighting back. In separate incidents, America's DirecTV and Spain's Canal Satelite Digital have broadcast codes to disable the hacked cards.

"It has become a very sophisticated battle," said Mr Stanyard.

Over the last year, DirecTV has been regularly sending small chunks of computer code out to smartcards. To stop them being remotely disabled, many cracked cards would not accept the data being sent out by DirecTV. But without updates, cards will no longer provide access to shows.

Hidden purpose

So crackers found ways to put the code updates on pirated cards and initially thought the regular updates were just meant to annoy and inconvenience them.

But on 21 January, the real purpose of the updates was revealed. Together, the seemingly unrelated chunks of code created a program that DirecTV used to zap the hacked cards.

The program put the card into a loop that made it impossible to update and change. Satellite card hacking sites on the web reported that the last few bytes of data had been changed to read "Game Over".

Channel stopping

Some estimate that 98% of DirecTV hacked cards have been knocked out, affecting as many as 100,000 illegal users.

"We took countermeasures to blackout unauthorised users," said Robert Mercer, a DirecTV spokesman. "If you have a counterfeit card, we'll find it and disable it." He said that it was not the first or last time that the company would use "electronic countermeasures" against unauthorised cards.

The second zapping attack by Spain's Canal Satelite Digital was less successful. Europe's satellite TV companies are plagued by piracy and it is estimated that up to 20% of Europe's 35 million satellite subscribers are pirates.

Mr Stanyard said the TV companies were in a difficult position because making better programmes cost money which forced up charges and made hacking more worthwhile.

The satellite station sent out the signal on Sunday night and did manage to zap the cards of hackers for a few hours. Unfortunately, soon after, the card crackers came up with a fix and it was soon widely available on hacking websites.

Card crackers are working on ways to get around the DirecTV zap attack but so far seem to be having little success. "It's a war," said Mr Stanyard, "and it's one that will go on forever."